The Portable Operating System Interface, commonly known as POSIX, is a set of standards designed to ensure compatibility between different operating systems. It defines the application programming interface (API), command line shells, and utility interfaces, allowing software developers to write applications that can run on various systems without modification. POSIX was developed by the IEEE and is widely used in Unix-like operating systems, including Linux and macOS. By adhering to these standards, developers can create portable applications that function consistently across different platforms, enhancing software interoperability and reducing development time.